Such conventional exhaust manifolds are disclosed in Japanese Patent applications Publication No. 2003-83062, No. 2005-307920 and No. 2003-83062, and they include a plurality of branch pipes that are connected with a head flange of an engine, and a collecting part that collects downstream side end portions of the branch pipes to be connected with a catalytic converter.
Further, in these conventional exhaust manifolds, as shown in FIG. 11, a reinforcement member 09, which is formed like a cross shape, is inserted in a space formed among downstream side end portions 02a to 05a of branch pipes 02 to 05, and they are fixed with one another by welding.